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Link between inner crater collapses, plume events and transient signals during the 2021 Geldingadalir eruption

Alea Joachim 1, Sebastian Heimann1, Eva P. S. Eibl1, Leah Rees1, Maximilian Dwars1, Egill Árni Gudnason2, Thorbjörg Ágústsdóttir2, Gylfi Páll Hersir3,4, Tom Winder4, Nicholas Rawlinson4, Tomáš Fischer5, Jana Doubravová6, Jan Burjánek6, Oliver D. Lamb7

  • Affiliations: 1Institute for Geosciences, University of Potsdam, Potsdam, Germany; 2 ISOR, Iceland GeoSurvey, Kópavogur, Iceland; 3Independent Researcher, Reykjavík, Iceland; 4University of Iceland, Reykjavík, Iceland; 5Faculty of Science,Charles University, Prague, Czechia; 6Institute of Geophysics, Czech Academy of Sciences, Prague, Czechia; 7Te Pū Ao GNS Science, Wairakei Research Centre, Taupō, New Zealand

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 107

  • Programme No: 2.1.17

  • Theme 2 > Session 1

Abstract

After 781 years of volcanic quiescence, the Geldingadalir eruption started in March 2021 on the Reykjanes Peninsula in southwest Iceland. Several seismometers and acoustic sensors located across the peninsula, recorded volcanic tremor generated by the eruption. In early May, the tremor pattern shifted from continuous to episodic, characterised by minute-long episodes followed by periods of repose. However, by mid-June, the continuous tremor reappeared but ceased abruptly in early July when the lava pond in the active crater drained completely. Two hours after the draining, a huge dark plume and a few smaller plumes appeared, which were accompanied by transient seismic signals and six distinct acoustic signals, whose peak tends to arrive before the seismic signal peak. After these plume events, the duration of tremor increased significantly, with episodes lasting for hours rather than minutes. Here, we study the role of these plume events in this tremor transition and analyse the cause of the seismic events and the plume events in detail. To analyse the seismic events, we performed a source inversion using seismometers within a 6 km radius of the active crater and tested different source models, including moment tensor and single force models. Additionally, we calculated a decreasing Volcanic Acoustic-Seismic Ratio (VASR) with time from the seismic and acoustic signals and we will discuss its potential interpretation. Using video data from local webcams, we analyse potential causes of these plumes, and we investigate a possible link between the observed plumes and the transient signals.